Radio compass



Feb- 24 1942- E. H. HuGENHoLTz RADIO COMPAS S Filed Nov. 13, 1939 3 Sheets-Sheet l ma WBD Gttorneg Feb. 24, 1942- E. H. HuGENHoLTz RADIO COMPASS Filed Nov. 13, 19:59

3 Sheets-Sheet 2 (Ittorneg Feb. 24, 1942.

E. H. HUGENHOLTZ RADIO COMPASS Filed Nov. 13, 1939 3 Sheets-Sheet 3 Patented Feb. 2d, i942 Uidi@ ETENTFTECE KABE() CMELSS (Cl. Z50-4.1)

(Granted under the provisions or' sec. 14, act of March 2, 1927; 357 O. G. 5)

lands, assigner to 4 Claims.

This invention relates to a radio compass of the known type, wherein the waves of the station whose bearings are to be taken are received in two loop aerials placed perpendicularly to one another (a so-called cross-loop) and ina fixed aerial without directional effect.

The invention has for its purpose a similar compass of such a construction that the direction of the waves incident on the cross-loops is immediately indicated by a measuring instrument.

The device with which this object is realized according to the invention operates in such manner that the two voltages supplied by the crossloops are successively modulated either before or after combination with a voltage which is taken from the aerial, by auxiliary voltages either of different phase or of different frequency. The two voltages thus modulated, if desired together with a voltage originating from the aerial, are so combined and detected that, when supplied to a measuring instrument, they give a direct indication of the angle at which the incoming waves reach the cross-loops.

If the compass is so designed that the two modulating auxiliary voltages are different in phase, the modulated loop voltages can, according to the invention, be combined with one another and with a voltage originating from the xed aerial, detected and supplied to a phase meter. The meter then gives a direct reading of the direction, since the direction becomes manifest as a phase difference between the mcdulated and detected voltage on the one side and the modulating auxiliary voltages on the other side.

If the two modulating auxiliary voltages are not different in phase but diiTerent in frequency. it is also possible to modulate after each of the two voltages from the loops first has been combined with a voltage originating from the red by reference to the accompanying drawings showing, by way of example, some embodiments of these tWo alternatives.

Figure 1 is a schematic circuit diagram of one embodiment of the invention; and Figures 2 and 3 are schematic circuit diagrams oi modified species of the invention. In describing the several gures of the drawings, similar reference numerals will be used to identify similar elerents.

Referring to the diagram of Fig. l, the Waves arriving from the station whose bearings are to be taken are received in cross-loop aerials I, 2 and in a nondirectional aerial 29. The currents of one loop l, which is struck by the incoming waves at an angle 0, are led along conductors 3, l to a centre-earthed primary inductor 5 which is coupled to a secondary inductor ii. The latter is interposed between earth and a control grid l' of a multielectrode tube B. The currents of the other loop 2 are led along conductors 9, Iii to a centre-earthed primary iriductor ll which '1s coupled to a secondary inductor l2, the latter being located between earth and a grid i3 ci a second electronic tube it which is similar to the tube S. In this way, the grid l has irnpressed on it a voltage which is equal to ein cos c cos wt, and the grid i3, a voltage equal to cm sin 6 cos et. The tube S is further provided with additional grids i5, l", ll and IS and with an anode IS. Between the latter I9 and the grid l5 is connected an output inductor 29 of the tube 8, said inductor being centretapped and the tap connected to the grid il of the tube 8 and to the positive pole of a source of direct current. The tube le has four additional grids 2l, 22, and 2li and an anode 25. The latter 25 is connected to the grid 2i through an output inductor 25. The centre of the output inductor 25 is connected to the centre of the output inductor Ztl and consequently also to the positive pole of the source of supply. The two output inductors 20 and 26 are inductively coupled to a third inductor 2'! which can be tuned by means of a variable condenser 33. The third inductor 2 is further connected to a fourth inductor 2B which is located in the lead between the aerial 2Q and earth. For the sake of simplicity, any elements serving to bring the voltages of the aerial and loops as much as possible in pbase have been omitted.

Between two terminals 3E! and 3 l across which a voltage Vm cos pt is established, is connected a primary 32 which is coupled to a secondary 33 which has one terminal connected to the second control grid I6 of the tube 8 and the other terminal to a point of negative potential. Between two additional terminals 35i, 35, across which a voltage Vm sin pt is established, is connected a primary t@ which is coupled through a secondary 37 to the second control grid 22 of the tube lfl. The output electrodes i5 and t9, and 2l and 25 form the balanced output circuits of balanced modulators in which the modulation voltages are applied to the intermediate grid electrodes I3 and 22 so that the carrier voltages are suppressed as inthe case of conventional balanced modulators. The alternating currents impressed on the first control grids of tubes 8 and I4 are thus modulated, with suppressed carrier waves, by the two voltages set up between 3U, 3I and 34, 35 respectively which may be, for example, low frequency voltages. Thus a voltage e'i cos 0 cos pt cos wt is impressed on the circuit 2l', 38 by means of the output inductor 25 and a voltage ez sin sin pt cos wt will be:

6{1-I-w cos (pt-0) }cos wt This voltage is set up at a grid 39 of a thermionic tube 45 and detected. A resistance 4I is connected in the output circuit of the tube 4i). The alternating current voltages produced across this resistance are supplied through a blocking condenser 43 to the moving coil of a measuring instrument 42. Furthermore, a rotation field is excited in this instrument with the Vaid of the two voltages Vm cos pt and Vm sin 'pt which are 90 different in phase. Since the current in the moving coil will be equal to im cos (pt-6), the pointer of the instrument 42 will adjust itself at an angle 0 and thus give a direct indication of the direction under which Waves of the station whose bearings are to be taken reach the loop I In the construction of Fig. 2, the signals to be received are modulated and combined in a circuit arrangement which initially is similar to that of Fig. 1. However, the terminals 3D and 3| have the alternating current voltage Vm cos pt applied to them, and the terminals 34 and 35, the alterhating current voltage Vm cos qt, consequently with a divergent frequency. A voltage is nowinduced in the circuit 21, 38 by the output inductor 20, which voltage is equal to e1 cos 0 cos pt cos wt. By the output inductor 26 is induced ez sin 6 cos qt cos wt and by the fourth inductor 28, ca cos wt. Postulating il... ca l and ea wz the circuit has a voltage produced in it which is equal to ea(1|-a1 cos 0 cos pt-l-az sin 0 cos qt) cos wt. After detection by the tube 40, the anode circuit has produced in it as an alternating current component of the detected current: ia w1 cos a cos pt-i-z'a wz sin 0 cos qt. This current flows through the primaries 63 and 65 and induces in the secondaries 64 and 56 a voltage: 6"(1 cos 0 cos pt-i-wz sin 0 cos qt). The reference numeral 45 indicates a lter which solely transmits alternating currents having the angular frequency p. An alternating voltage c1" cos 0 pt will then be set up between the output terminals of the filter 45. By means of a primary coil 52, a voltage is induced in a secondary coil 53 equal to Vm cos pt. Taking it: 1 l

then at the rectfying tube 45 is established a voltage Vm 1+1 cos 0) cos pt. The potential of the direct current across a resistor 41 brought about by detection becomes Vm(1+1 cos 0). Furthermore, the alternating current voltage Vm cos pt is detected by the rectifying tube 5I This supplies a direct current having a potential Vm across a resistor 49. If Vm is sufciently constant, the compensation voltages Vm obtained in this case by detection may also be derived without further means from the source of direct current. A direct current of potential Vml cos 0 is set up as a difference between the conductors leading from 43 and 4l' to the instrument 42, if the internal resistance of the instrument is very high. Y

'I'he alternating voltages set up across a coil 65 are supplied to a lter 54 which exclusively transmits alternating currents having the angular frequency q. Consequently, an alternating Voltage e2" sin H cos qt is set up between the output terminals of the filter 54. of a primary coil 62, a voltage (Vm cos qt) is induced in a secondary coil 5I.

Taking there is set up at the rectifying tube 55 a voltage: Vm(1|2 sin 0) cos qt. The potential of direct current across a resistor 5t produced by detection becomes Vm(1|2 sin 0). Moreover, the alternating voltage Vm cos qt is detected by the rectifying tube 60. This supplies a direct current of potential Vm across a resistor 58,.

A direct current Vmz sin eis set up as afpotential difference between the conductors leading from the resistor 56 and the resistor58 to an indicating instrument 42, if the internal resistance of the instrument is very high. IfV the instrument 42 is, for example, a cross-coil instrument,.it will immediately indicate the angle 0, if i=2- In the example of Fig. 3, the high frequency alternating current induced in the first loop I is induced in the inductor 6 by means of an inductor 5, so that the Voltage e1=em cos 0 cos wit is set up at the grid l. Moreover, the alternating current generated in the aerial 29 supplies a current through inductors 28 and l2. A. Voltage ea cos wt is thus induced by the inductor 'IZinan inductor 'I3 coupled thereto. 1n this case, any elements which may be required for obtaining the exact phase between the alternating currents of the aerial and loops are not shown.

Taking the alternating voltage set up at the grid 'I can be represented by the expression: eaG-I-w cos 6) cos wt. Furthermore, the alternating voltage Vm cos pt is induced at grid i6 of the tube 8 by the coupled inductors 32 and 33 with the result that in the tube the alternating vo-ltage set up at the grid 'I is modulated by said voltage to obtain a suppressed carrier wave. Due to the anode current of the tube 8, a voltage e(1-Iw cos 0) cos pt cos wt is induced in coil 2l by coil 20.

The alternating current induced in the other loop 2 supplies an alternating Voltage e2=em sin 6 cos wt on grid I3 of tube I4 through the couvpled inductors II and I2. Moreover, at this grid Moreover, by means is also set up the E. M. F. es cos wt induced in inductor 13. The total alternating voltage set up at grid i3 can be represented by the expression: ea (1+i: sin 0) cos wf. The alternating voltage Vm cos qt is induced by inductors 3S and 31 on grid 22 of tube Id. In the tube, the alternating current Voltage set up at grid I3 is modu lated by said alternating voltage to obtain a suppressed carrier wave. Due to the anode current of tube Hl, there is induced in inductor 21 by inductor 26: e (l-i-w sin 0) cos qt cos wt. Further, a voltage e cos wt derived from the aerial is induced in inductor 21 by inductor 2%. Taking nthennthe total voltage induced in the circuit 21, 38 can be represented by the expression: e(1+,8 (l-i-w cos 6) cos pt-i- (l-l-w sin 0) cos qt) cos wt. This alternating Voltage is set up at the grid of tube B8 and supplies as detection result an anode current: im (l-i- (l-l-w cos 6) cos 'pH- (l-l-w sin 0) cos qt). This current induces corresponding alternating currents in coil 64 by coil S3 and in coil 56 by coil 65. By 45 is again designated a filter designed in such manner that it exclusively transmits alternating currents having an angular frequency p. Consequently, an alternating Voltage according to the expression em (l-i-w cos cos pt is set up at the rectifying tube 48. The potential of the direct current across the resistance 41 produced by rectification is according to the expression Vm (l-l-w cos 0). The alternating current across the circuit 21, 38 is, in addition, rectied by a tube 61 in series with a resistor 10. Bry a proper choice of the various magnitudes, it can be ensured that the rectied Voltage across the resistor is exactly Vm. Between the conductors leading from resistors 41 and 1l] to the meter 42, is now set up the difference of the voltages across those resistors, i. e., Vm (l-l-w cos 0) Vm-:Vm w cos 0. If 42 represents a cross-coil instrument, this voltage consequently is set up across the one coil. The voltage induced in coil 66 is set up at the lter 54 which again exclusively transmits voltages having the angular frequency q. The rectifying tube has now applied to it an alternating voltage according to the expression: em (l-l-w sin 0) cos qt. A direct current of potential Vm (l-l-w sin 0) is produced across the resistor 69 by rectification. Between the conductors leading from the resistors 69 and 10 to the meter 42, there is produced a voltage difference: Vm (1+w sin 6) Vm=Vm w sin 0. This voltage is set up at the cross-coil of the instrument. The instrument indicates the angle 0 by combination. It should be understood that any antenna system having crossed patterns of the type produced by crossed loops may be substituted for the crossed loop system. For example, Adcock antennas or dipoles may be used.

I claim as my invention:

1. A radio compass having a pair of crossed directional antennas and a nondirectional antenna, means for modulating with distinctive currents the currents derived from waves intercepted by said directional antennas, means including at least a portion of said modulating means for suppressing the currents corresponding to the carrier frequency of said waves, means for deriving a current from said nondirectional antenna, means for combining the current from said antenna with said currents less said currents of carrier frequency derived from said directional antennas, means for detecting the thus modulated and combined currents, means for rectifying the detected currents, means for rectifying the modulating currents, means for combining the rectified detected currents and the rectified modulating currents to form two currents bearing directional information, a directional indicator, and means for applying the said two currents bearing directional information to said indicator to indicate the angle between the said wave fronts and one of said directional antennas.

2. A radio compass having a pair of crossed directional antennas and a nondirectional antenna, means for modulating with currents of different frequency the currents derived from Ywaves interceptednby said directional antennas,V

means for deriving a current from said nondirectional antenna, means for combining the current from said antenna with said currents derived from said directional antennas, means for detecting the thus modulated and combined currents, means for rectifying said detected currents, means for rectifying the modulating currents of different frequency, means for combining the rectied detected currents and the rectified modulating currents, a directional indicator, and means for applying the two combined rectied currents to said indicator to indicate the angle between the said wave fronts and one of said directional antennas.

3. A radio compass having a pair of crossed directional antennas and a nondirectional antenna, means for modulating with currents of different frequency the currents derived from waves intercepted by said directional antennas, means for deriving a current from said nondirectional antenna, means for combining the current from said antenna with said currents derived from said directional antennas, means for detecting the thus modulated and combined currents, a filter for separating the currents of different frequencies after detection, means for rectifying the separated currents, means for rectifying said modulation currents of dierent frequencies, means for combining the rectified detected currents with the rectified modulation currents to form two currents, a directional indicator, and means for applying the two combined rectified currents to said indicator to indicate the angle between the said waves and one of said directional antennas.

4. A radio compass having a pair of crossed directional antennas and a nondirectional an- 7 tenna, means for modulating with currents of dierent frequency the currents derived from waves intercepted by said directional antennas, means for deriving a current from said nondirectional antenna, means for combining the current from said antenna with said currents derived from said directional antennas, means for detecting the thus modulated and combined currents, a filter for separating the currents of different frequencies after detection, means for rectifying the separated currents, means for sepa rately rectifying said modulation currents of different frequencies, means for combining the rectied detected currents with the rectified modulation currents to form two currents, a directional indicator, and means for applying the two combined rectied currents to said indicator to indicate the angle between the said wave fronts and one of said directional antennas.

EDUARD HERMAN HUGENHOLTZ. 

